I. Field of the Invention
This invention relates generally to articulated trailers towed by a tractor or draft vehicle. In particular, the present invention relates to articulated trailers that use multiple pivoting sections to facilitate cornering. Known prior art relevant to the invention disclosed herein can be found in U.S. Patent Class 280 in the various subclasses found thereunder.
II. Description of the Prior Art
As recognized by those skilled in the trailer arts, effective cornering of lengthy trailers is often a dangerous and difficult task. The prior art is replete with devices that are designed to make cornering lengthy trailers safe. One approach uses a pivoting front axle to turn the front end of the trailer.
The known prior art discloses several arrangements that steer the front wheels of an articulated trailer. The wheels of some of these steerable axles may even be locked in a "straight ahead" position to facilitate backing of the trailers.
However, these devices generally do not turn sharp corners well because the trailer front axle pivots as the draft vehicle turns. This premature pivotal movement often results in the trailer cutting across the corner. This can cause serious damage to the trailer or to objects adjacent the corner (i.e., curbs, stop signs, automobiles, people, etc.).
Another approach to the cornering problem is to split a long trailer into two separate, smaller trailers. Normally, these smaller trailers are connected by assemblies that are commonly known as dollies. Thus, the two small trailers may be towed by one draft vehicle.
U.S. Pat. No. 4,768,802 teaches a steerable dolly having a steering linkage that turns the dolly wheels relative to the dolly frame. A steering linkage facilitates the steering of the dolly depending upon the yaw articulation angle of the configuration. The steering ratio may be manually reduced by reducing the effective length of one of the links on the steering linkage.
Another invention directed toward dolly steering is shown in U.S. Pat. No. 3,995,876. This invention uses the dolly to support and steer the front end of the trailer during backing operations. The dolly is rigidly attached to a small tow vehicle that manipulates the trailer. The assembly increases the maneuverability of the trailer in tight areas. This invention is primarily directed at improving the backing up of the trailer.
U.S. Pat. No. 4,645,226 discloses a dolly that maintains a flexible and rigid sideways connection between the dolly assembly and a lead trailer. This invention is directed at reducing the occurrence of jackknifing during braking or maneuvering.
However, most dolly type devices suffer from problems with controlling the trailers during braking and maneuvering. Thus, dollies do not solve the cornering problem efficiently.
Several known, prior art trailer hitches that utilize multiple connecting points between the draft vehicle and the trailer are of general relevance. These patents include U.S. Pat. Nos. 3,787,068, 3,790,191, 4,405,147, and 3,582,110. All of these devices utilize multiple hitches that have attachment points at or near the leading edge of the trailer.
Several interesting devices are disclosed in U.S. Pat. Nos. 4,111,451, 4,650,205, 4,597,585 and 4,993,738. These devices are of general relevance to the invention disclosed herein but are directed to different structures that solve other problems.
Other patents of lesser relevance include U.S. Pat. Nos. 4,111,450 and 4,768,801. These patents deal with inventions wherein the rear axle of the trailer is designed to pivot. U.S. Pat. No. 4,215,874 discloses a method of pivoting the front and rear frames of the trailer during turning.
I am the named inventor on U.S. Pat. No. 5,295,703. This patent discloses an articulated trailer for sail boats. In that invention, the jack assembly suspends the front axle of the trailer in a locked position out of contact with the ground. A pivoting jack wheel permits the trailer to be steered like a single axle trailer to back the trailer more efficiently.
U.S. Pat. No. 3,556,558 discloses a dual pivoting hitch that attaches a trailer to a draft vehicle. The hitch automatically, mechanically pivots about two points to permit the more effective control of the trailer and to permit sharper turns. This patent does not teach a method of controlling the transfer of angular movement between the two pivot points.
The known prior art fails to adequately address the problem associated with efficiently turning lengthy trailers. The prior art also fails to provide a method of offsetting or swinging a trailer wide in anticipation of sharp turns. Another problem the prior art also fails to address is the need for an easily offset trailer wherein the trailer may be articulated so that it does not directly follow the draft vehicle. An improved trailer would also need to provide an efficient method for orienting the direction of travel of the trailer when backing. An ideal configuration would permit selective, directional trailer movement regardless of the rearward movement of the draft vehicle.
Therefore, a trailer wherein the angular direction of the front axle relative to the draft vehicle is controllable is desirable. Another desirable function of the trailer would be a user selectable guide that ensures the direction of rearward movement of the trailer during backing. My trailer provides the desirable features of a single axle trailer coupled with the desirable features of a articulated trailer.